U.S. patent number 7,449,234 [Application Number 10/443,779] was granted by the patent office on 2008-11-11 for sliding material.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha, Mitsubishi Chemical Functional Products, inc.. Invention is credited to Toshihiro Fukagawa, Yu Murai, Akira Obara, Tetsuya Ogawa, Satoshi Takesako, Satoshi Yoshida.
United States Patent |
7,449,234 |
Fukagawa , et al. |
November 11, 2008 |
Sliding material
Abstract
A sliding material consisting of a carbon-fiber reinforced
carbon composite material containing fine particles of a simple
substance of any of Group IV to Group VI elements or a carbide, a
nitride or an oxide thereof.
Inventors: |
Fukagawa; Toshihiro (Kagawa,
JP), Obara; Akira (Kagawa, JP), Ogawa;
Tetsuya (Tochigi, JP), Yoshida; Satoshi (Tochigi,
JP), Murai; Yu (Tochigi, JP), Takesako;
Satoshi (Tochigi, JP) |
Assignee: |
Mitsubishi Chemical Functional
Products, inc. (Tokyo, JP)
Honda Giken Kogyo Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
19194752 |
Appl.
No.: |
10/443,779 |
Filed: |
May 23, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20040005462 A1 |
Jan 8, 2004 |
|
Foreign Application Priority Data
|
|
|
|
|
May 24, 2002 [JP] |
|
|
2002-151461 |
|
Current U.S.
Class: |
428/317.9;
188/250R; 188/251A; 188/251R; 192/107M; 192/70.14; 428/316.6;
428/323; 428/325; 428/408; 428/698 |
Current CPC
Class: |
C04B
35/63496 (20130101); C04B 35/83 (20130101); C04B
41/009 (20130101); C04B 41/5057 (20130101); C04B
41/5068 (20130101); C04B 41/87 (20130101); F16D
69/023 (20130101); C04B 41/5057 (20130101); C04B
41/4539 (20130101); C04B 41/4556 (20130101); C04B
41/5068 (20130101); C04B 41/4539 (20130101); C04B
41/009 (20130101); C04B 35/83 (20130101); C04B
2111/00353 (20130101); C04B 2111/00362 (20130101); C04B
2235/3826 (20130101); C04B 2235/3839 (20130101); C04B
2235/3847 (20130101); C04B 2235/386 (20130101); C04B
2235/3886 (20130101); C04B 2235/404 (20130101); C04B
2235/48 (20130101); C04B 2235/5445 (20130101); C04B
2235/77 (20130101); C04B 2235/80 (20130101); C04B
2235/96 (20130101); Y10T 428/249986 (20150401); Y10T
428/249981 (20150401); Y10T 428/31504 (20150401); Y10T
428/25 (20150115); Y10T 428/252 (20150115); Y10T
428/30 (20150115) |
Current International
Class: |
B32B
5/22 (20060101); F16D 13/00 (20060101) |
Field of
Search: |
;428/317.9,319.1,312.2,323,325,408,698,316.6 ;192/70.14,107M
;188/250R,251R,251A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
25 01 870 |
|
Sep 1975 |
|
DE |
|
36 22 437 |
|
Oct 1987 |
|
DE |
|
197 11 829 |
|
Sep 1998 |
|
DE |
|
100 48 764 |
|
Apr 2002 |
|
DE |
|
0 300 756 |
|
Jan 1989 |
|
EP |
|
0 507 564 |
|
Oct 1992 |
|
EP |
|
2 626 570 |
|
Aug 1989 |
|
FR |
|
1 475 237 |
|
Jun 1977 |
|
GB |
|
3-12377 |
|
Jan 1991 |
|
JP |
|
3-12378 |
|
Jan 1991 |
|
JP |
|
3-197377 |
|
Aug 1991 |
|
JP |
|
6-345570 |
|
Dec 1994 |
|
JP |
|
7-101783 |
|
Apr 1995 |
|
JP |
|
10-194877 |
|
Jul 1998 |
|
JP |
|
Other References
Translation of JP 10-194877, Sogabe et al, "Tungsten-Carbon
Composite Material," Jul. 28, 1998. cited by examiner .
Translation of JP 06-345570, Akihiro Kuroyanagi, "Production of
Axidation Resistant C/C Composite Material," Dec. 12, 1994. cited
by examiner.
|
Primary Examiner: Vo; Hai
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, P.C.
Claims
What is claimed is:
1. A sliding material comprising a combination of a disk substrate
and a pad configured to slide against each other, wherein the disk
substrate comprises a first carbon-fiber reinforced carbon
composite material containing fine particles consisting of hafnium
carbide having an average particle size of at least 0.01 .mu.m and
at most 10 .mu.m, where the content of the fine particles is at
least 0.01 wt % and at most 1 wt % of the total weight of the first
carbon-fiber reinforced carbon composite material; and the pad
comprises a second carbon-fiber reinforced carbon composite
material that does not contain hafnium carbide particles.
2. The sliding material according to claim 1, wherein the bulk
density of the first carbon-fiber reinforced carbon composite
material ranges from 1.5 to 2.2 g/cm.sup.3.
3. The sliding material according to claim 1, wherein the porosity
of the first carbon-fiber reinforced carbon composite material
ranges from 3 to 25 vol %.
4. The sliding material according to claim 1, wherein the fine
particles are supported in the inside with a distance of at least 1
mm and at most 10 mm from the surface of the first carbon-fiber
reinforced carbon composite material.
5. The sliding material according to claim 1, wherein the first
carbon-fiber reinforced carbon composite material has a densified
matrix which is a pitch, a resin or a CVD carbon.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sliding material consisting of a
carbon-fiber reinforced carbon composite material having a high
friction coefficient and excellent wear resistance.
2. Description of the Background
A carbon-fiber reinforced carbon composite material (hereinafter
referred to simply as C/C composite material) is usually produced
by impregnating or mixing a resin to a carbon fiber aggregate,
followed by heating forming, or by baking a carbon fiber structure
(carbon fiber preform) in a non-oxidizing atmosphere and densifying
it, followed by graphitizing treatment as the case requires. The
C/C composite material has conventionally been used as a material
for e.g. sliding members, drive joints or braking mechanism, as a
material which has a high specific strength, which is light and
which can be used at a high temperature. It has attracted attention
particularly as a sliding material for e.g. a brake and clutch of
aircraft, public vehicles and racing vehicles.
When the C/C composite material is used as a sliding material, it
is used under heavy load conditions of high temperature and high
pressure, and accordingly various methods to increase the friction
coefficient and wear resistance have been proposed.
Among them, many methods to cover the surface of the C/C composite
material with a SiC layer by means of e.g. a vapor-phase growth
method such as a CVD method, a coating method or an impregnation
method, have been proposed. However, although the sliding material
obtained by this method has improved wear resistance, it tends to
have a low friction coefficient. Further, its bulk density tends to
be high, thus impairing weight savings, and further, the production
costs tend to be high.
On the other hand, it has been known that a sliding material
excellent in wear resistance can be obtained by a method of adding
fine particles of an inorganic substance having a Knoop hardness of
at least 300 kg/mm.sup.2 to a carbon fiber preform, followed by
forming, baking and densifying (JP-A-7-101783). However, although
the sliding material obtained by this method has improved wear
resistance, the improvement of the friction coefficient is
insufficient.
In a case where the C/C composite material is used as a sliding
material for e.g. a brake or clutch, particularly as a brake
material or a clutch material for racing vehicles, a sliding
material having a high friction coefficient is required for
deceleration in a short time or so as to decrease the sliding area.
Further, at the time of sliding under a heavy load, the temperature
of the sliding material tends to be high, and the friction
coefficient tends to decrease by fading, such being problematic.
Thus, it is an object of the present invention to provide a sliding
material consisting of a C/C composite material which is light and
excellent in wear resistance, and which has a high friction
coefficient even under a heavy load.
SUMMARY OF THE INVENTION
The present invention has been accomplished as a result of
extensive studies to overcome the above problems, and it resides in
a sliding material consisting of a carbon-fiber reinforced carbon
composite material containing fine particles of a simple substance
of any of Group IV to Group VI elements or a carbide, a nitride or
an oxide thereof. Group of elements is described in Mendeleev's
periodic table.
Now, the present invention will be described in detail with
reference to the preferred embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The sliding material of the present invention consists of a C/C
composite material having fine particles of a specific inorganic
substance added thereto. The C/C composite material itself is
usually produced by a conventionally known method except that
specific fine particles are added thereto, and its type is not
particularly limited.
Further, as the material carbon fibers, pitch based carbon fibers,
polyacrylonitrile based carbon fibers or rayon based carbon fibers
may be used. As the preform of carbon fibers, various preforms such
as a one-dimensionally oriented preform, a two-dimensionally woven
laminated preform such as plain weave, stain weave or woven fabric,
a two-dimensional non-woven preform which is two-dimensionally
randomly oriented, a three-dimensionally oriented preform, a felt
and a tow may be employed. The C/C composite material is produced
by densification/heat treatment of such a preform, and as the
densifying matrix, a resin, pitch or CVD carbon may, for example,
be used, and one type or several types of densifying matrices may
be combined.
The resin used as the densifying matrix may, for example, be a
phenol resin, a furan resin or an epoxy resin, and a phenol resin
having a high carbonization yield is particularly preferred. When
pitch or CVD carbon is employed as the densifying matrix, it may be
either isotropic or anisotropic. The C/C composite material is
produced by applying a heat treatment at a temperature of usually
at least 1,000.degree. C., preferably at least 1,300.degree. C.,
and usually at most 3,000.degree. C., preferably at most
2,400.degree. C., during the densification until the final stage.
The bulk density of the C/C composite material is usually from 1.5
to 2.2 g/cm.sup.3, preferably from 1.6 to 2.0 g/cm.sup.3, and the
porosity is usually from 3 to 25 vol %, preferably from 5 to 20 vol
%.
The sliding material of the present invention is obtained by
incorporating the following fine particles of an inorganic
substance into the above C/C composite material by an optional
method. The inorganic substance is a simple substance of any of
Group IV to Group VI elements or a carbide, a nitride or an oxide
thereof. Among them, hafnium, tantalum or tungsten or a carbide, a
nitride or an oxide thereof is particularly preferred, and among
them, preferred are hafnium, hafnium carbide, hafnium oxide,
tungsten, tungsten oxide, tungsten carbide and tantalum, and
particularly preferred are hafnium carbide, tungsten and tantalum.
The fine particles may be of a combination of several types.
The particle size of the fine particles is usually at least 0.01
.mu.m, preferably at least 0.1 .mu.m, and usually at most 10 .mu.m,
preferably at most 5 .mu.m, particularly preferably at most 1
.mu.m. To improve the friction coefficient and to reduce the wear
loss of the sliding material, the additive is present preferably in
the form of fine particles as far as possible. It is estimated that
the additive present on the sliding area grinds the C/C composite
material substrate as an abrasive component, and the grinding
resistance increases the friction coefficient, however, the degree
of grinding of the C/C composite material substrate tends to be
significant when the particle size of the additive is large, thus
increasing wear. Accordingly, if the particle size is larger than
10 .mu.m, not only the wear tends to be significant, but also
addition to the carbon-fiber reinforced carbon composite substrate
tends to be nonuniform, and particularly when the fine particles
are impregnated to the pores of the carbon-fiber reinforced carbon
composite substrate, the fine particles are less likely to enter
the pores. On the other hand, if the particle size is smaller than
0.01 .mu.m, not only the effect of reduction of wear tends to be
small, but also the cost to pulverize the fine particles tends to
be high. The particle size means a number average particle size as
measured by a laser method.
The method of incorporating the above fine particles into the C/C
composite material is not particularly limited. The fine particles
may be supported by a carbon fiber preform or a carbon fiber
prepreg, either during the densification step or after completion
of the densification. However, to support the fine particles by a
preform or a lowly densified product, the fine particles are
required to be fixed by e.g. a resin so as to prevent the supported
fine particles from dropping, since the number of pores of the C/C
composite material is large, and the fine particles easily drop.
Further, as the C/C composite material is produced by a heat
treatment at a high temperature, the properties of the fine
particles may change by the heat treatment depending upon the type
of the fine particles. Thus, preferred is a method wherein
densification and the heat treatment are completed to obtain the
C/C composite material, and then its pores are impregnated with the
fine particles.
For example, the following method may be mentioned. The C/C
composite material is immersed in a solvent having fine particles
of an inorganic substance dispersed therein, the gas present in
pores in the inside of the C/C composite material is removed, and
the pores in the inside of the C/C composite material are
impregnated with the fine particles and the solvent, and then the
solvent is removed, followed by drying. Further, a baking treatment
may be carried out after the drying as the case requires. The
amount of the fine particles dispersed in the solvent may be
adjusted depending upon the amount of the pores in the C/C
composite material preliminarily measured and the aimed amount of
impregnation. An appropriate solvent used for impregnation is one
which will not remain in the carbon-fiber reinforced carbon
composite substrate after drying, and a solvent having a boiling
point of at most 200.degree. C., for example, water, an alcohol
such as ethanol or propanol or a glycol may be employed. Further,
in order to increase dispersibility of the fine particles, a
viscosity improver such as polyethylene oxide may be added to
adjust the viscosity of the solvent.
The content of the fine particles is usually at least 0.01 wt %,
preferably at least 0.1 wt %, and usually at most 3 wt %,
preferably at most 1 wt %, of the total weight of the C/C composite
material. If it is less than 0.01 wt %, no adequate effect will be
obtained, and if it exceeds 3 wt %, not only friction among the
fine particles will take place, thus decreasing the friction
coefficient, but also addition and impregnation of the fine
particles into the C/C composite material tend to be difficult in
some cases.
Further, the fine particles are preferably supported in the
vicinity of the surface of the carbon-fiber reinforced carbon
composite material, and they are preferably impregnated and
supported in the inside with a distance of at least 1 mm,
preferably at least 3 mm and at most 10 mm, from the sliding
surface. In a case of impregnation with a distance of less than 1
mm, no effect of impregnated fine particles will be obtained when
the thickness of the sliding material is reduced to less than 1 mm
by wear due to friction. Further, impregnation with a distance
exceeding 10 mm is hardly achieved in a case of a C/C composite
material having a high degree of densification, and usually a
thickness of the part to be used as a friction material of at most
10 mm is sufficient in many cases.
When the sliding material consisting of a specific C/C composite
material of the present invention comprises a disk and pads, the
fine particles may be contained in either or each of the disk and
the pads. When the fine particles are contained in each of the disk
and the pads, the type of the fine particles contained in the disk
and the pads may be the same or different.
Now, the present invention will be described in further detail with
reference to Examples. However, it should be understood that the
present invention is by no means restricted to such specific
Examples.
EXAMPLE 1
A densifying step of impregnating a three-dimensional preform (bulk
density: 0.45 g/cm.sup.3) of PAN type carbon fibers with pitch,
followed by baking, was repeatedly carried out, followed by a heat
treatment at 2,000.degree. C. to obtain a C/C composite material
having a porosity of 10 vol % and a bulk density of 1.80 g/cm.sup.3
The C/C composite material was formed into a disk brake shape with
an outer diameter of 274 .phi., immersed in a mixed solution of
water and isopropanol (weight ratio of 7:3, density of liquid:
0.94) containing 2.9 wt % of HfC having an average particle size of
0.9 .mu.m and 0.1 wt % of polyethylene oxide, the pressure was
reduced to at most 50 Torr and then the pressure was recovered to
normal pressure, so that the C/C composite material was impregnated
with the HfC particles and the solvent. Then, the solvent was
removed by drying. The operation of impregnation and drying was
repeated twice to obtain a disk brake having the C/C composite
material impregnated with HfC in an amount of 0.3 wt % based on the
C/C composite material. This disk brake was cut in half and
observed by a stereoscopic microscope, whereupon it was confirmed
that the HfC fine particles adequately entered at least up to a
portion with a distance of 3 mm from the sliding surface.
On the other hand, a densifying step of impregnating a
three-dimension preform of the same PAN type carbon fibers as the
disk with pitch, followed by baking, was repeatedly carried out,
followed by a heat treatment at 1,600.degree. C. to obtain a pad
made of a C/C composite material having a porosity of 13 vol % and
a bulk density of 1.70 g/cm.sup.3.
The above obtained disk/pads made of the C/C composite material was
subjected to a friction test under conditions of an average
rotational speed of the sliding area of 30 m/s, a sliding area
pressure of 300 PSI, an absorbed energy (disk) per unit area of 750
J/cm.sup.2, and as a result, the average friction coefficient was
0.49, the wear rate of the disk was 8.7.times.10.sup.-4
mm/stop/surf., and the wear rate of the pad was 8.7.times.10.sup.-4
mm/stop/surf. The above results are shown in Table 1.
COMPARATIVE EXAMPLE 1
A disk and pads made of a C/C composite material were produced in
the same method as in Example 1 except that the disk of Example 1
was not impregnated with HfC. The evaluation results of the same
friction test as in Example 1 are shown in Table 1.
COMPARATIVE EXAMPLE 2
A C/C composite material disk substrate obtained in the same method
as in Example 1 was impregnated with SiC having an average particle
size of 1.0 .mu.m in an amount of 0.36 wt % to obtain a disk brake.
It was combined with the same pads as in Example 1, and the
evaluation results of the same friction test as in Example 1 are
shown in Table 1.
COMPARATIVE EXAMPLE 3
A C/C composite material disk substrate obtained in the same method
as in Example 1 was impregnated with BN having an average particle
size of 1.0 .mu.m in an amount of 0.2 wt % to obtain a disk brake.
It was combined with the same pads as in Example 1, and the
evaluation results of the same friction test as in Example 1 are
shown in Table 1.
TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 1 Ex. 2 Ex. 3
Type of fine HfC Nil SiC BN particles Group of fine Group IV --
Group XIV Group XIII particles Average particle 0.9 -- 1.0 1.0 size
of fine particles (.mu.m) Content in disk 0.3 0 0.36 0.2 (wt %)
Content in pad (wt %) 0 0 0 0 Friction coefficient 0.49 0.44 0.40
0.43 Wear rate of disk 8.7 7.7 7.8 7.7 (.times.10.sup.-4
mm/stop/surf.) Wear rate of pads 8.7 11.5 7.5 11.0
(.times.10.sup.-4 mm/stop/surf.)
EXAMPLE 2
A C/C composite material disk substrate obtained in the same method
as in Example 1 was impregnated with W having an average particle
size of 0.6 .mu.m in an amount of 0.7 wt %, followed by a heat
treatment at 1,600.degree. C. so that W and the C/C composite
material substrate were reacted to obtain a disk brake. The
obtained C/C composite material disk was cut into half and observed
by a SEM-EDX (scanning electron microscope-energy dispersive X-ray
analyzer), whereupon W atoms were adequately detected at least up
to a portion with a distance of 3 mm from the sliding surface.
Further, the C/C composite material disk was analyzed by means of
X-ray diffraction, whereupon peaks of WC and W.sub.2C were detected
in addition to a peak of carbon. Pads were prepared by repeatedly
carrying out a densifying step of impregnating a two-dimensional
preform (bulk density: 0.63 g/cm.sup.3) of PAN type carbon fibers
with pitch, followed by baking, and then carrying out a heat
treatment at 2,000.degree. C. to prepare a substrate having a
porosity of 16 vol % and a bulk density of 1.65 g/cm.sup.3. The
pads were not impregnated, and combined with the disk impregnated
with W, and the same friction test as in Example 1 was carried out.
The evaluation results are shown in Table 2.
COMPARATIVE EXAMPLE 4
A disk and pads made of a C/C composite material were produced in
the same method as in Example 2 except that the disk of Example 2
was not impregnated with W. The same friction test as in Example 2
was carried out. The evaluation results are shown in Table 2.
TABLE-US-00002 TABLE 2 Comparative Example 2 Example 4 Type of
inorganic fine W Nil particles Group of inorganic fine Group VI --
particles Average particle size of fine 0.6 -- particles (.mu.m)
Content in disk (wt %) 0.7 0 Content in pad (wt %) 0 0 Friction
coefficient 0.52 0.50 Wear rate of disk 18 29 (.times.10.sup.-4
mm/stop/surf.) Wear rate of pad 94 111 (.times.10.sup.-4
mm/stop/surf.)
EXAMPLE 3
A C/C composite material disk substrate obtained in the same method
as in Example 1 was impregnated with Ta having an average particle
size of 0.6 .mu.m in an amount of 0.28 wt %, followed by a heat
treatment at 1,600.degree. C. so that Ta and the C/C composite
material substrate were reacted to obtain a disk brake. The
obtained C/C composite material disk was cut into half and observed
by a SEM-EDX (scanning electron microscope-energy dispersive X-ray
analyzer), whereupon Ta atoms were adequately detected at least up
to a portion with a distance of 3 mm from the sliding surface.
Further, the C/C composite material disk was analyzed by means of
X-ray diffraction, whereupon a peak of TaC was detected in addition
to a peak of carbon. As pads, a densifying step of impregnating a
two-dimensional preform (bulk density: 0.63 g/cm.sup.3) of PAN type
carbon fibers with pitch, followed by baking, was repeatedly
carried out, followed by a heat treatment at 1,600.degree. C. to
prepare a substrate having a porosity of 15 vol % and a bulk
density of 1.67 g/cm.sup.3. The pads were not impregnated, and
combined with the disk impregnated with Ta, and the same friction
test as in Example 1 was carried out. The evaluation results are
shown in Table 3.
EXAMPLE 4
A C/C composite material disk substrate obtained in the same method
as in Example 3 was impregnated with TiN having an average particle
size of 1.0 .mu.m in an amount of 0.26 wt % to obtain a disk brake.
It was combined with the same pads as in Example 3 and the same
friction test as in Example 3 was carried out. The evaluation
results are shown in Table 3.
EXAMPLE 5
A C/C composite material disk substrate obtained in the same method
as in Example 3 was impregnated with MoC having an average particle
size of 1.0 .mu.m in an amount of 0.35 wt % to obtain a disk brake.
It was combined with the same pads as in Example 3 and the same
friction test as in Example 3 was carried out. The evaluation
results are shown in Table 3.
COMPARATIVE EXAMPLE 5
A disk and pads made of a C/C composite material were produced in
the same method as in Example 3 except that the disk of Example 3
was not impregnated with Ta. The same friction test as in Example 3
was carried out. The evaluation results are shown in Table 3.
TABLE-US-00003 TABLE 3 Comp. Ex. 3 Ex. 4 Ex. 5 Ex. 5 Type of
inorganic fine Ta TiN MoC Nil particles Group of inorganic Group V
Group IV Group VI -- fine particles Average particle size 0.6 1.0
1.0 -- of fine particles (.mu.m) Content in disk (wt %) 0.28 0.26
0.35 0 Content in pad (wt %) 0 0 0 0 Friction coefficient 0.53 0.51
0.50 0.48 Wear rate of disk 49 115 183 120 (.times.10.sup.-4
mm/stop/surf.) Wear rate of pad 29 48 56 50 (.times.10.sup.-4
mm/stop/surf.)
According to the present invention, a sliding material consisting
of a carbon-fiber reinforced carbon composite material having a
high friction coefficient can be provided without impairing wear
resistance.
The entire disclosure of Japanese Patent Application No.
2002-151461 filed on May 24, 2002 including specification, claims
and summary is incorporated herein by reference in its
entirety.
* * * * *